Metabolic Bone Disorders

Abstract

Metabolic bone diseases are a group of disorders caused by alterations in the chemical milieu of the body. In almost all cases, the end result is decreased skeletal mass. This is known as osteopenia or, in its more pronounced form, osteoporosis. Severe osteoporosis can lead to structural failure of the skeleton. This concept of organ failure is just as valid in the skeletal system as it is in the heart, the kidney, etc. Early stages of metabolic bone disease may be difficult to diagnose because 30% of the bone mass must be removed before the change can be appreciated on plain radiographs. Therefore, patients may be evaluated with a DEXA scan, a very sensitive radiographic study which determines bone loss. Metabolic bone disease may be divided into four categories: focal osteoporosis, specific endocrine abnormalities, primary osteoporosis, and secondary osteoporosis. Focal osteoporosis results from disuse of the skeleton. This may be of a single extremity or it may be of the entire skeleton. Traumatic disorders or joint disease may lead to non-weight bearing, and this may cause decrease in bone mass. Weight bearing and the use of the skeleton is necessary to preserve healthy bones. This is mediated by electric potentials which are generated when the bone is deformed during use. Total osteoporosis may result from prolonged bed rest or weightless environments.